Nom du directeur de thèse: Fabienne Michelini

Tel : 04 13 94 53 17

E-Mail:: fabienne.michelini@univ-amu.fr

Laboratoire: IM2NP

Financement: demandé

Type de financement: contrat doctoral

Summary in English :

The outstanding performance of biological functions makes living organisms extremely attractive for inspiring the design of new generations of ingenious, sustainable and efficient technologies, eagerly awaited in the global context of climate change.

Here is the case of photosynthesis. In the early stages of this biological function, photon energy is collected by antennas before being transferred to the reaction centres where the charges are separated and used in the chain of chemical reactions that make life on earth possible [1].  These antennas and reaction centres are nanometre-sized molecular assemblies that form transport networks for charges and energy. The efficiency of photon-charge conversion is very close to 100% in these networks. This efficiency is so high that the photosynthetic function also includes the evacuation of excess energy in case of high light intensity [2].

At the state of the art, our understanding of these natural processes and the origin of their performance remains incomplete, in particular on how the system simultaneously exploits its electronic and structural dynamical properties to harvest, transfer but also dissipate energy in cooperation with its environment. Most of the existing theoretical work is based on approaches combining molecular dynamics with semi-classical kinetics or master equations in the quantum regime, but very few address the energy transport properties [3,4]. However, the initial processes of photosynthesis are basically ultra-fast transport phenomena, from a hundred femtoseconds to a hundred picoseconds, taking place at the nanometric scale. These processes therefore belong to the field of mesoscopic physics, and fall within the scope of quantum transport. This field has already proved to be adapted to the modelling and simulation of nanodevices. Actually, this change of viewpoint should contribute to understanding the exceptional performance in photosynthesis, and thus to developing a bio-inspired conception of sustainable and high-performance nanotechnologies for the conversion of light energy [5].

The thesis project is part of this research dynamics with the strong objectives of:

• implementing a methodology for living organisms using quantum transport tools based on the formalism of time-dependent out-of-equilibrium Green functions [6,7],
• understanding the roles played by quantum coherence, coupling to the environment, in particular the bath formed by vibrations, as well as the impact of time-dependent variations of these couplings.
• bridging this knowledge to the field of nanotechnology by imagining original systems for producing energy from nanometric hybrid assemblies based on nanostructures, 2D materials, and organic molecules.

Références

1. Scholes, G. D.; Fleming, G. R.; Olaya-Castro, A.; van Grondelle, R. “Lessons from nature about solar light harvesting”, Nature Chemistry 2011, 763–774.
2. Pinnola A.; Bassi R. “Molecular mechanism involved in plant photoprotection”, Biochemical Society Transaction 2018, 46, 467-482.
3. Zerah-Harush, E.; Dubi, Y. "Universal Origin for Environment-Assisted Quantum Transport in Exciton Transfer Networks”, The Journal of Physical chemistry Letters 2018, 9, 689– 169.
4. Fassioli, F.; Olaya-Castro, A.; Scholes, G. D. “Coherent Energy Transfer under Incoherent Light Conditions”, The Journal of Physical Chemistry Letters 2012, 3, 3136–3142.
5. Brédas, J.-L.; Sargent, E. H.; Scholes, G. D. "Photovoltaic concepts inspired by coherence effects in photosynthetic systems," Nature Materials 2017, 35–44.
6. Beltako, K., Michelini, F., Cavassilas, N., and Raymond, L. “Dynamical photo-induced electronic properties of molecular junctions,” J. Chem. Phys. 148(10), 104301 (2018).
7. Michelini, F. and Beltako, K. “Asymmetry induces long-lasting energy current transients inside molecular loop circuits,” Physical Review B 100(2), 024308 (2019).

Candidate skills required :

The desired candidate must have a profile as an inorganic or organic condensed matter physicist or biophysicist, with numerical know-how and with a background in mechanics or quantum chemistry.